The present invention relates generally to apparatus and methods for inserting vascular catheters into blood vessels and, more particularly, to the construction and use of a guiding catheter for selectively directing such catheters to particular blood vessels.
A wide variety of non-invasive angioplastic methods exist for removing obstructions from blood vessels. Generally, these methods rely on the peripheral introduction of a catheter to the site of the obstruction and the manipulation of the catheter in some manner to remove the obstruction. The most common method employs a balloontipped catheter which is inflated at the site of the obstruction to dilate the passage therethrough. Also, laser catheters are used to ablate obstructions, and certain catheters are then provided with cutting implements to excise the obstructions.
One difficulty with such angioplastic techniques has been the ability to properly locate a catheter within the patient's vascular system. A common approach to this problem is to place the catheter with a steerable guidewire. Typically, the guidewire includes a spring tip which is bent so that the direction of insertion can be selected by rotating the wire. The catheter, which includes a central or guidewire lumen, is then inserted over the guidewire to the proper location. Alternatively, some catheters have an integral spring tip which is used to guide the catheter in an analogous manner.
Not all catheters are well suited for placement using guidewire techniques however. Some angioplasty catheters and other therapeutic modalities (e.g., fluted cutters), for example, lack a guidewire lumen. Since these devices cannot accommodate a guidewire, they must be placed using other techniques.
Alternate means for positioning vascular catheters are known. For example, special catheter have been devised for positioning vascular catheters and other therapeutic modalities within a particular vessel. These guiding catheters or catheter guides typically include a central lumen which accommodates a vascular catheter. In operation, the guide is first positioned within the vessel of interest, typically with the aid of fluoroscopy. The central lumen of the guide is often used for injecting contrast media so that the lesion of the vessel may be concurrently visualized. Once the guide is properly positioned, a therapeutic catheter may be readily advanced to the lesion by passing it through the central lumen.
Other means for positioning vascular catheters are known. U.S. Pat. No. 4,769,005, for example, describes a guiding sheath for inserting guidewires or vascular catheters within a blood vessel which includes an elongate body having a plurality of axial lumens. The insertional sheath includes a primary axial lumen which is used for inserting the sheath onto a guidewire to locate where a branch in the vascular system occurs. Under fluoroscopic guidance, the sheath is positioned so that one of the lumens is properly located to direct the guidewire or catheter in the desired direction. U.S. Pat. No. 4,405,314 also describes an insertional catheter which provides for selective insertion of catheters into arteries.
The use of positioning devices, such as catheter guides and the like, incurs a significant penalty however. Due to their relatively large size, these devices often impede blood flow through the vessels in which they are inserted. For example, guiding catheters used for coronary angioplasty often impede blood flow through the ostium of a coronary artery.
The problem of maintaining blood flow (and hence preventing ischemia) with guiding catheters has been largely solved by adding side holes which allow self-perfusion of the vessel. This solution, however, has created another problem. While self-perfusing guides function well to maintain blood flow, they are poorly adapted for angiography techniques because large amounts of contrast media are typically lost to the surrounding vasculature. In particular, it is desirable to deliver contrast media through the distal end of the guide, which is positioned proximate a lesion; delivery of contrast media to other locations serves only to interfere with angiography.
With prior art guiding catheters, contrast media preferentially exits through the perfusion holes during its injection. Thus, a significant if not substantial amount of contrast media is delivered to a vessel which is not of particular interest (e.g., contrast media is delivered to the aorta during imaging of coronary arteries). As a result, the angiographic image is degraded, the risk of contrast toxicity is increased, and expensive contrast media is wasted. All three factors combine to greatly increase the overall cost and morbidity of using catheter guides.
Thus, it is highly desirable to provide apparatus and methods for the improved placement of vascular catheters and the like within the vascular system without increased risks from ischemia or excess contrast media. In particular, it is desirable to provide a guiding catheter which can facilitate the positioning of catheters to specific branches within the vascular system with the aid of angiographic techniques; concurrently, the guiding catheter should maintain perfusion while preventing loss of contrast media. Additionally, it is desirable to provide a guiding catheter which can stent a vessel. Particularly, when a dissection or flap occurs within a vessel (e.g., left main or proximal coronary artery), the catheter should be able to be placed in the area of disruption to permit continual perfusion of the distal vascular bed (temporary stent) until more definitive therapy can be undertaken. The present invention fulfills this and other needs.